The Trump administration is touting a drop in enforcement actions along the U.S.-Mexico border for a fourth straight month as proof it is successfully reducing illegal immigration into the United States.

The agency reported intercepting 52,546 people at the southwest border in September, including unauthorized crossings as well as those deemed inadmissible at legal border crossings. That constituted a 63% reduction from the 144,255 people apprehended or turned back in May, the highest monthly total of the 2019 fiscal year, which ended last month.

Declining numbers coincided with the Trump administration's implementation of policies restricting access to asylum that have prompted outcries from human rights advocates.

Earlier this year, the administration began forcing asylum-seekers and other migrants to await their U.S. immigration court dates in Mexico. Under the Migrant Protection Protocols, also known as the "Remain in Mexico" policy, more than 50,000 individuals have been returned across the border.

US Government's 'Remain in Mexico' Plan Sparks Tension and Confusion Teaser Description Migrants fleeing poverty and the threat of violence have found themselves caught up in fast-shifting US immigration and asylum laws

Meanwhile, the administration has forged agreements designating El Salvador, Guatemala and Honduras as asylum destinations, while stipulating that non-Mexicans must seek asylum in a third country they transited en route to the U.S. border before filing a claim in the United States.

Morgan said the policies were needed to curtail "numbers [of border arrivals] that no immigration system in the world is designed to handle, including ours."

Immigrant rights advocates, however, see a humanitarian disaster in the making.

"The new asylum rule is sufficient to stop almost everyone," said Helena Olea, an international human rights lawyer and adviser to Alianza Americas, a network of Latin American and Caribbean immigrant organizations in the United States.

Of concern, she said, are the "extremely weak asylum procedures" in Central American countries, "because no one is seeking protection in countries from which everyone is fleeing."

Families, mostly from Central America, but increasingly from outside the Americas, accounted for most of the spike in arrivals at the U.S.-Mexico border earlier this year.

At US-Mexico Border, Africans Join Diversifying Migrant Community While the overwhelming majority of these families continue to be from Mexico and the Northern Triangle, a small but growing proportion are from countries outside the Americas, nearly twice as much as two years ago

CBP has not released a detailed breakdown of data for September. It is unclear what proportion of those encountered by the agency last month were families, unaccompanied children, or adults traveling alone.

The drop in arrivals coincided with the hottest months at the U.S.-Mexico border. Immigration experts say the numbers could rise again as temperatures moderate.

Immigration advocates say factors compelling people to flee their home countries continue unabated.

"People may continue trying to cross," Alianza Americas' Olea said. "They may fail, but that doesn't mean they won't continue attempting to come to the U.S."